I recently tried out xen with m$$ installed but I was unable to find any info on how to boot m$$ directly with an entry from grub without having to load and start a trillion linux services.

Virtualbox with all the guest addition had m$$ 7 stalling several times something doesn't happen with xen. With xen the only slow part is the mouse, probably a graphic adapter, and low screen resolution.

But I needed it to run in a somewhat exclusive fashion, without and full blown linux os running underneath.

As far as I know qemu-kvm is not capable of booting directly to a virtual machine, vbox is out of the question. With xen I wasn't able to find anything references online. The current solutions concentrate on having m$$ being run with gfx card inside linux.

that's the idea to have a grub option that goes directly to the virtual machine. Looking around I can't see anything with virtualbox, qemu or xen. The closest thing I've see was a gdm/kdm entry to the virtual machine using virtualbox that way bypassing full-blown desktop underneath.

Possibly the kdm option is what seems to be closest thing for qemu and virtualbox, with xen it appears that something more minimal could be used.